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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 1:07 am 
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Yes, please post the voltages on the 6Q7 and 6F6 tubes.

It is not uncommon for a resistor to drift upwards over 2x in value. But I don't understand the color bands you listed of "red, yellow, red, green." Vintage resistors typically have only a 3-color code.

Matt


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 1:16 am 
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Posts: 1901
I will take a pic of it tomorrow and which other point should that resistor have connected to because it was on what was the end of a electrolytic that was cut off and all connecting points left intact


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 2:19 am 
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spsquires wrote:
which other point should that resistor have connected to

Here is a perfect opportunity to practice your schematic-reading skills. I count 13 components that connect to that end of R10. See if you can list them all.

Matt


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 12:30 pm 
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here is the voltages 6q7 pin3 92dcv pin4 minus 1.6dcv pin6 minus .4dcv pin7 6.1acv 6q7 pin3 264dcv pin4 286dcv pin6 91dcv pin7 6.1acv pin8 22dcv 6q7 tube in corner of chassis pin3 264dcv pin4 286dcv pin6 344dcv pin7 6.1acv pin8 22dcv and this is all voltages recorded


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 12:57 pm 
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here is the picture of the resistor and I will look at schematic later I have to work for a while


Attachments:
DSC00138.JPG
DSC00138.JPG [ 37.19 KiB | Viewed 433 times ]
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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 4:49 pm 
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That resistor uses the "body, end, stripe" color code. Red (2), green (5), yellow (0000) = 250000 ohms or 250k.

The tube voltages look ok to me. I don't see any reason why the audio would be cutting in and out. The last two tubes should be 6F6, not 6Q7.

Matt


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 5:54 pm 
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Location: Powell River BC Canada
spsquires wrote:
here is the voltages 6q7 pin3 92dcv pin4 minus 1.6dcv pin6 minus .4dcv pin7 6.1acv 6q7 pin3 264dcv pin4 286dcv pin6 91dcv pin7 6.1acv pin8 22dcv 6q7 tube in corner of chassis pin3 264dcv pin4 286dcv pin6 344dcv pin7 6.1acv pin8 22dcv and this is all voltages recorded



There is a problem if the last tube is a 6F6.


pin 3 ( plate) is higher than pin 4 (screen).

If the correct power transformer AND speaker are installed:
plate (3) 225 V screen (4) 240 V

Screen voltage is dropped through the field.

Given a new power transformer with higher voltages: the transposing of
screen and plate connections returns to the speaker wiring:

Where the schematic is the only wiring published, and no pictorial
is given, frequently out routing of the B+ to external wired devices
leads to many problems with restorers.


Attachment:
marconi 160 revisited field wires.JPG
marconi 160 revisited field wires.JPG [ 27 KiB | Viewed 417 times ]

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Amateur Radio Literacy Club. May we help you read better.
Steve Dow
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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 6:17 pm 
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Steve, I think you misread the voltages that Squires posted. For both 6F6 tubes, the plate (pin 3) is at 264V and the screen (pin 4) is at 286V. No problem with these voltages.

Matt


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 8:13 pm 
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so w.hat would you suggest next . is it possible a bad volume or tone control they both seem to have quite a bit of movement on the shaft


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 9:33 pm 
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Check resistance of R6 and R11. Note: One end of R6 should be grounded. A connection dot is missing in the schematic, see below.

Normally you can tell a bad volume or tone control from intermittent sound when you adjust the control. Are you noticing that?

Also, still waiting on your list of components connected to the other side of R10.

Attachment:
ground connection.jpg
ground connection.jpg [ 136.34 KiB | Viewed 401 times ]

Matt


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 9:59 pm 
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r-6 is 15.96 m ohms and r-11 is .609m ohms and r-6 has one side grounded


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 10:21 pm 
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also has I look at the radio c-18 should connect to pin 5 of 6a8 and go to ground correct


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 10:33 pm 
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here is the list not sure but hope I did ok r-12;first if ; second if ;c-28 ; c-30 ; c-19 ;r-8 ;c-39 ;r-2 ;c-17 ;band selector ; bias cell ; r-4


Last edited by spsquires on Jan Fri 13, 2017 10:38 pm, edited 1 time in total.

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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 10:33 pm 
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here is the list not sure but hope I did ok r-12;first if ; second if ;c-28 ; c-30 ; c-19 ;r-8 ;c-39 ;r-2;c-17 ;band selector ; bias cell ; r-4


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 11:01 pm 
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You got off to the right start but then you got lost.

r-12 - yes
first if - yes
second if - yes
c-28 - yes
c-30 - no
c-19 - no
r-8 - yes
c-39 - no
r-2 - no
c-17 - no
band selector - no
bias cell - no
r-4 - no

Print out the schematic and use a highlighter. Start from the bottom end of R10 and trace the wires. If the wires cross, they are not touching unless you see a dot there. Don't forget to include tube pins in the list. Try again.

Also, counting each IF transformer as 1 component, there are only 11 total instead of 13. (I was counting the cap and coil in each IF separately.)

Matt


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 11:09 pm 
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Joined: Mar Fri 07, 2014 10:20 am
Posts: 1901
I will try again but is my question about c-18 correct thanks


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 11:11 pm 
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Location: Powell River BC Canada
skylerca wrote:
Steve, I think you misread the voltages that Squires posted. For both 6F6 tubes, the plate (pin 3) is at 264V and the screen (pin 4) is at 286V. No problem with these voltages.

Matt


The voltage relationship between the plate and screen in the 159/160 Marconi, has the plate
higher than the screen.

Is the speaker/output transformer the original for the set?

_________________
de
VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
Steve Dow
ve7aso@rac.ca


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 11:15 pm 
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spsquires wrote:
I will try again but is my question about c-18 correct thanks

C18 is not present in your radio. Remember our discussion earlier:

skylerca wrote:
Ok, the schematic is different from your radio. On your radio, the 6A8 cathode (pin 8) is grounded, but on the schematic it is connected to ground through C18 and R13. I am guessing this was a production change and you have the earlier version of the radio. Let's try to get the radio working as is. Later we may want to add C18 and R13.

Matt


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 Post subject: Re: marconi model 160
PostPosted: Jan Fri 13, 2017 11:25 pm 
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here is another try r-12 ; first if; second if ;c-28 ; r-8 ;pin 4 6f6 ; output transformer ;pin3 6q7 ;c-25 ;c-26 ;c-29


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 Post subject: Re: marconi model 160
PostPosted: Jan Sat 14, 2017 12:22 am 
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r-12 - yes
first if - yes
second if - yes
c-28 - yes
r-8 - yes
pin 4 6f6 - yes
output transformer - yes
c-29 - yes
pin3 6q7 - no
c-25 - no
c-26 - no

You're almost there. Pin 3 of 6Q7 and C25 and C26 are all connected to the top end of R10. We are just looking at connections to the bottom end of it.

Also, I was counting pin 4 of each 6F6 tube separately, so if you count those as one you just have two left to go.

Hints: Tube near R8, and component near output transformer.

Matt


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